How does lipophilicity (logP) influence tissue distribution and the volume of distribution?

How does lipophilicity (logP) influence tissue distribution and the volume of distribution?

• A. Higher logP decreases membrane permeability and reduces tissue partitioning, lowering Vd.
• B. Higher logP increases membrane permeability and tissue partitioning, often increasing Vd due to distribution into fat and other tissues.
• C. logP has no effect on tissue distribution or Vd.
• D. Lower logP increases Vd by promoting adipose partitioning.

Answer: (B)

Lipophilicity, expressed as logP, reflects how soluble a drug is in fats versus water. When a drug is more lipophilic (higher logP), it crosses lipid membranes more readily and distributes into tissues more extensively. This tissue distribution pulls drug molecules out of the plasma and into fat and other tissues, which lowers the concentration in the blood for a given dose and raises the apparent volume of distribution (Vd). In other words, a highly lipophilic drug tends to have a larger Vd because it sequesters in tissues rather than remaining confined to the plasma. If a drug is less lipophilic, it stays more in the aqueous compartments (plasma and extracellular fluid), leading to a smaller Vd. This explains why lipophilic drugs often show higher Vd values, especially when adipose tissue is a major reservoir. So, higher lipophilicity increases membrane permeability and tissue partitioning, often increasing Vd due to distribution into fat and other tissues.

Lipophilicity, expressed as logP, reflects how soluble a drug is in fats versus water. When a drug is more lipophilic (higher logP), it crosses lipid membranes more readily and distributes into tissues more extensively. This tissue distribution pulls drug molecules out of the plasma and into fat and other tissues, which lowers the concentration in the blood for a given dose and raises the apparent volume of distribution (Vd). In other words, a highly lipophilic drug tends to have a larger Vd because it sequesters in tissues rather than remaining confined to the plasma.

If a drug is less lipophilic, it stays more in the aqueous compartments (plasma and extracellular fluid), leading to a smaller Vd. This explains why lipophilic drugs often show higher Vd values, especially when adipose tissue is a major reservoir.

So, higher lipophilicity increases membrane permeability and tissue partitioning, often increasing Vd due to distribution into fat and other tissues.